Spark distance

Schlag-versuch, m. impact test, percussion test, -wasser, n. bilge water, -welte, /. striking distance (of an electric spark), spark distance. -werk, n. striking appparatus, specif, rammer signal bell, -wetter, n. pi. fire damp. 

Two other useful parameters related to capacitive sparks and dust ignitions are (i) the optimum sparking distance is 10 mm and (ii) the quenching distance is 7 mm. Refer to Sec. 4.1 and Table 5, where MIE is discussed in more detail. 

El. Earhart, R. F., The sparking distances between plates for small distances, Phil. Mag. 1, 147 (1901). 

A spark is a non-self-sustaining axe discharge. The distance, at atmospheric pressure, over which a spark can occur for a given voltage is called the spark distance. For air, typical values are around 20 cm for a voltage of 105 V. A well-known example of spark is lightning, which is believed to be the longest (tens of kilometres) known spark. 

The dielectric cohesion of argon is 38, ranking next to helium and neon. The sparking distance in argon is about 40 per cent greater than in air. A phosphorescence similar to that obtained in neon has been observed. 

Wire sparklers are wires coated with pyrotechnic composition which are hand-held and produce a gende spray of gold sparks from iron filings. Fountains are cardboard tubes filled with chemical mixtures that produce a spray of color and sparks extending 2—5 m into the air. Roman candles are cylindrical tubes which repeatedly fire colored stars distances of 5—20 m into the air. These items typically contain 5—12 stars. 

Flame plating (D-gun) employs oxygen and fuel gas. In this method, developed by the Union Carbide Corporation, the gas mixture is detonated by an electric spark at four detonations per second. The powders, mixed with the gas, are fed under control into a chamber from which they are ejected when detonation occurs. The molten, 14—16-pm particles are sprayed at a velocity of 732 m/s at distances of 5.1—10.2 cm from the surface. The substrate is moved past the stationary gun. 

For a line spark source, the flame volume is initially cylindrical with the cylinder length equal to the separation distance between the electrodes. Thus, for a cylindrical flame, = e, and the critical ignition volumes are equation 7 for a spherical flame and equation 8 for a cylindrical flame where = critical ignition volume, m /kg e = thickness of flame front, m and d = flame height, m. 

There were several studies of hydraulic transport in the 1950s, sparked off particularly by an interest in the economic possibilities of transportation of coal and other minerals over long distances. Newitt et al.p2) working with solids of a range of particle sizes (up to 5 fim) and densities (1180-4600 kg/m3) in a 25 mm diameter pipe, suggested separate correlations for flow with a bed deposit and tor conditions where the particles were predominantly in heterogeneous suspension. 

Sparks due to static electricity associated with the separation of two dissimilar materials (Table 5.5). The charges may be transported/conducted some distance after separation before there is sufficient accumulation to produce a spark, e.g. in the flow of liquids or... 

A spark is generated between two conductors when the distance between the conductors is small compared to the diameter of the conductors and when the electric field intensity between the conductors is approximately 3 MV/m. A brush discharge is generated if the distance between the conductors is large compared to the radius of curvature of the conductor. 

Minimum Spark Ignition Energies and Quenching Distances... 

Fig. 2.3 Rate-limiting steps in mineral dissolution (a) transport-controlled, (b) surface reaction-controlled, and (c) mixed transport and surface reaction control. Concentration (C) versus distance (r) from a crystal surface for three rate-controUing processes, where is the saturation concentration and is the concentration in an infinitely diluted solution. Reprinted from Sparks DL (1988) Kinetics of soil chemical processes. Academic Press New York 210 pp. Copyright 2005 with permission of Elsevier...

For a fixed distance, sparking occurs at a critical voltage leading to smoke, flame, flash, crackling, decomposition, ignition or explosion. This critical voltage is a measure of electric spark or electrostatic discharge sensitivity of the explosive under test [71-73]. 

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